The present invention relates to the mounting of motor vehicle wheels, and in particular, to a motor vehicle wheel which is mounted on an axle hub and retained by a single self-locking central nut.
The present invention is particularly adapted to a passenger vehicle and will be described with specific reference thereto; however, it will be apparent that the invention has broader applications and may be employed for mounting the wheels of other types of vehicles wherein quick and simplified mounting and secure retention of the wheel is desired.
Typically, the wheel of passenger vehicles are attached to the axle by means of a plurality of mounting studs and lug nuts. The axle includes an outwardly projecting annular hub which is telescoped through a central opening in the wheel and serves to concentrically locate the wheel with the axis of axle rotation. The studs are attached to an axle flange in a circumferentially spaced pattern and project through a corresponding socketed hole pattern in the wheel. In assembly, the lug nuts are tightened by a conventional wrench to clamp the wheel between the lug nuts and the axle flange, thereby axially retaining and providing torque transmission to the wheel. For mounting and removal of the wheel for repair or replacement, each of the lug nuts must be removed.
Where speed of wheel change is important, such as race cars and the like, central nut wheel mountings are commonly used. In these constructions, the wheel hub includes an exterior thread which projects outwardly beyond the wheel hub. A central nut having an interior thread is threaded over the hub and provides the sole clamping force for retaining the wheel on the hub. The torque transmission is provided by axially projecting drive pins received within aligned holes in the wheel. Such central nuts may be provided with a hexagonal shape for tightening with a conventional socket wrench or may be provided with a plurality of radially projecting arms which are impacted by a mallet or like device for tightening or loosening the nut. Such central nuts, unless sufficiently torqued, are prone to loosening under driving conditions leading to a loss of wheel stability and loss of wheel retention under adverse conditions. Central nut wheel mountings are also becoming increasingly popular with automotive enthusiasts. The performance, styling and other benefits of such wheel mountings make the centrally retained wheel an attractive option or modification for passenger vehicles. Therein, an adapter is fixedly mounted on an axle hub using the existing studs and lug nuts. The adapter has an outwardly projecting annular hub for positioning the wheel and an outboard threaded end which receives the central nut. The adapter includes axial drive pins which engage recesses in the wheel to transfer torque to the adapter and through the studs to the axle. Inasmuch as these drive pins are normally located on the same diameter as the lug nuts, there is the possibility that the wheel may be mounted with the lug nuts on the wheel recesses. The heads of the lug nuts are not intended for direct drive transmission and may fail under high loading conditions. Further, because these operators are not as experienced as racing personnel, not as fully aware of the installation requirements or may not have sufficient strength or proper equipment for the installation, the potential for inadequate tightening and consequent loosening of the nut is increased. To guard against the loosening of the nut, numerous approaches have been taken to secure the nut to the adapter. For instance, the nut and the adapter may have alignable holes through which safety pins or safety wires may be attached. With such an arrangement, when the nut is at an acceptable installation torque, it is further rotated until the holes in the nut and the adapter are aligned. However, at these torque levels, it is difficult to align the holes at this single alignment position. Moreover, the additional tightening may increase the force required to remove the nut detracting from the mounting advantages of the system. Further, the difficulty in obtaining alignment may cause the operator to forego the locking device when alignment problems are encountered. While additional holes may be provided to provide for finer adjustment, this increases the cost of the assembly while not significantly reducing the installation and removal time and its complexity. Thus, the need exists for a simplified central nut wheel mounting for passenger vehicles which is readily installed and wherein the central nut is securely locked to the adapter hub and which remains so locked until removal is desired.